It is useful to prioritize installation of certain important prefixes, like DNS server IPs, company portal, etc to make sure Your customers can at least reach Your company portal to read messages about outages should they happen.
This "high" priority is not related with route prefrence. Its related with route installattion order on the local router.
In case of network convergence low priority prefixes are installed only after the high priority prefixes in the routing table. These priorities can be applied via an import policy. Routes that are not explicitly assigned a priority are treated as medium priority.
If you want to see this in action you can perfrom routing restart or anything else that you would trigger network convergance. It won't have any imact in steady state.